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Main Panel Upgrade for Solar in Visalia & Tulare County

We do main panel upgrades for solar around Visalia and Tulare County: the 120 percent rule, main-breaker derate, solar-ready panels, supply-side connections, and battery hookup. We coordinate with your solar installer and file the utility interconnection on the electrical side.

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Written by Cen Cal Electricians, Visalia, CA. Updated . How we write these pages

What we do

  • Main panel upgrade sized for a solar backfeed
  • Main-breaker derate when the load calculation allows it
  • Solar-ready and center-fed panel installation
  • Supply-side (line-side) connections when the drawing calls for them
  • Battery, gateway, and critical-loads panel hookup
  • Busbar math against the 120 percent rule, in writing
  • Permit and SCE or PG&E interconnection paperwork
  • Coordination with your solar installer on one set of drawings

Signs the panel, not the roof, is the bottleneck

  • The solar drawing shows a backfeed larger than the busbar can take under the 120 percent rule.
  • The main is center-fed or the bus is already full of tandems.
  • You are adding a battery and the gateway needs a different service equipment lineup.
  • The existing can is Federal Pacific, Zinsco, or a fuse box.
  • The solar installer asked for a derate, a new solar-ready panel, or a supply-side tap.

How the job goes

  1. Send the solar drawing

    Tap Get help now. Attach the one-line or the installer proposal and a photo of the panel label. Inverter current and bus rating are the first two numbers we need.

  2. Busbar math and site visit

    We apply the 120 percent rule, then look at derate vs a new solar-ready panel vs a supply-side connection. You get that choice in writing before anyone orders a can.

  3. Permit and utility interconnection

    We pull the electrical permit and file the SCE or PG&E interconnection that sits on the electrical side. The solar installer files the generation side. We keep those packets aligned.

  4. Swap, then the array

    The panel, derate, or supply-side connection happens before, or with, the inverter landing. The inspector sees a finished, labeled service. The utility grants permission to operate after their review.

What changes the price

Every bid starts with a look at the site. These are the things that move the number.

  • Derate vs a full panel swap vs a supply-side connection.
  • Whether a battery gateway or a critical-loads panel is in the same visit.
  • Meter-main location, stucco, and working space at the service.
  • SCE vs PG&E equipment lists and interconnection steps.
  • Whether the existing can is an obsolete brand that has to go anyway.

Notes for the Central Valley

  1. Valley roofs take a lot of sun, so array sizes here often outgrow a 200A bus with a 200A main under the 120 percent rule. That is a panel conversation, not a module conversation.

  2. New SCE and PG&E solar customers sit on the Net Billing Tariff, often called NEM 3.0. Storage changes the value of midday production. Grid-tied solar without a battery still shuts off in an outage.

  3. SCE and PG&E set their own interconnection timelines and publish their own queues. We file the electrical packet and track it with the installer.

The 120 percent rule, in plain English

A grid-tied solar inverter feeds a breaker in your panel. That breaker and the main breaker both dump current onto the same busbar. The California Electrical Code (based on the NEC) limits that combination. The common form, often called the 120 percent rule, says the main breaker plus the solar breaker cannot exceed 120 percent of the busbar rating.

Example, not a quote: a 200A bus with a 200A main leaves 40A for a backfed solar breaker (200 × 1.2 − 200 = 40). A larger solar array may not fit. That is a panel problem, not a roof problem.

  • Main-breaker derate

    Sometimes we install a smaller main breaker on the same bus, which frees room for a larger solar breaker, if the load calculation still supports the house. This only works when the math and the panel listing allow it.

  • Solar-ready or center-fed panel

    Some panels are listed to take a 200A main plus a larger solar breaker because of how the bus is built. A solar installer will often spec this. We install the panel that the one-line drawing calls for.

  • Supply-side connection

    A supply-side (line-side) connection taps the service before the main breaker. It has its own code rules, working space, and utility requirements. It is not a shortcut around a bad busbar. We use it when the drawing and the inspector expect it.

Batteries, NEM 3.0, and the solar installer

New SCE and PG&E solar customers fall under California's Net Billing Tariff, often called NEM 3.0. Exported solar earns less than it did under older plans, so storing midday solar in a battery for the evening is worth more. Grid-tied solar without a battery still shuts off in an outage. See home battery backup.

We coordinate with your solar installer. They size the array and the inverter. We own the panel, the derate or swap, the backup gateway or critical-loads panel, the permit, and the utility interconnection paperwork that sits on the electrical side. One set of drawings, one inspection sequence, fewer surprises on swap day.

Send the solar drawing and a photo of the panel label. We size the electrical work from those documents and give you a written price after we see what the bus and the main can take.

Where we do this work

We take this work within about 60 miles of Visalia, in towns such as Visalia, Farmersville, Tulare, Dinuba, Woodlake, and Lindsay. Each town page names the permit office and the utility, and lists other local shops. See every town.

Questions people ask

What is the 120 percent rule?

It is the common name for a California Electrical Code limit on how much current a panel busbar can take from the main breaker plus a backfed solar breaker. On a 200A bus with a 200A main, that often leaves 40A for solar. A larger inverter needs a derate, a solar-ready panel, or a supply-side connection.

What is a main panel derate?

Installing a smaller main breaker on the same bus to free room for a larger solar breaker, if the load calculation still supports the house and the panel listing allows it. It is not always available, and it is not a way around a panel that should be replaced.

Do I need a panel upgrade for solar?

Only if the busbar math, the main type, or the condition of the can requires it. Some houses take solar on the existing panel. Some need a derate. Some need a new solar-ready can or a supply-side connection. The drawing decides it.

Do you install batteries too?

We do the electrical work: panel, gateway, critical-loads panel, and interconnection. Send the solar drawing and a photo of the panel label so we can confirm what that side needs. See our home battery backup page for the storage-side path.

Who pulls the permit and talks to SCE or PG&E?

We pull the electrical permit. Interconnection is split: we handle the service equipment packet, the solar installer handles the generation packet, and we keep the two aligned so the inspector and the utility see one job.

Send the solar drawing and the panel photo

Tap Get help now. Cen Cal Electricians reads every request and replies within 24 hours.

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